This invention relates to disinfection of surgical equipment, specifically electronic equipment used in surgical procedures. As used herein, the terms "sterilization" and "disinfection" are essentially equivalent, although "sterilization" generally is understood to imply the destruction of all biological material on the items sterilized, while "disinfecting" means killing all pathogenic life forms, apart from certain bacteria in spore form. The methods and apparatus of the invention are useful for both.
Increasingly, surgical procedures are performed using probes inserted into the body of a patient, as such "minimally-invasive" procedures are safer, less traumatic, and less costly than traditional open techniques. Examples of such minimally-invasive probes include endoscopic instruments for forming a visual image of a body joint, organ, or the like to be examined, as well as various types of probes for performing angioplasty and similar procedures, and ultrasonic probes for imaging body parts. Many such probes include a cable comprising a number of electric conductors for carrying signals to and from a probe head at the distal tip of the probe. This application specifically discusses ultrasonic probes, but it is to be understood that the invention claimed herein also relates to electronic probes as employed for other purposes.
In most circumstances of use, electronic probes used in surgical procedures are connected to external equipment by a multiple-conductor cable. In the example of an ultrasonic probe, such external equipment provides a drive signal to a transducer in a probe head to cause it to emit ultrasonic energy traveling into a body part to be examined. The external equipment similarly includes devices for processing return signals provided by the transducer at the probe head, responsive to detection of the ultrasonic energy after reflection within the body part to be imaged. To carry these drive and return signals, a number of conductors must be provided running along a multi-conductor cable between the external equipment and the transducer at the head of the probe. Accordingly, the complete probe comprises a probe head, including the transducer, and a multi-conductor cable, terminated by a multi-pin connector, by which the probe is connected to external equipment for providing the drive signal and processing the return signal, and also including various storage and display devices. An intermediate cable may be provided between the multi-pin connector terminating the probe cable and the external equipment.
It is essential to either sterilize the probe or to prevent contact between an unsterilized probe and the patient. There are currently available no fully satisfactory methods of sterilizing delicate surgical devices, such as probes incorporating electronic equipment.
Normal surgical disinfection and sterilization processes involve exposure of the entire probe, comprising the probe head, the cable and, preferably, the multi-pin connector terminating the cable, to a room-temperature disinfecting medium, either fluid or gas. Room-temperature disinfecting media are desirably employed for disinfection of electronic surgical equipment, as such equipment is vulnerable to elevated-temperature autoclaving or steam disinfection processes.
Disinfection of an electronic probe comprising a cable terminated by a multi-pin cable connector poses several difficulties. If the connector's contacts are exposed to and wetted by disinfecting fluids, they may corrode, interfering with their proper connection. Accordingly, a common practice is to place a fluid-tight protective cap over a ferrule in the connector housing extending around the contacts, so as to seal the contacts from the disinfecting medium. However, such caps are often lost. The cap can be retained on the cable by a flexible plastic member, chain, or the like, but this tends to be cumbersome and annoying.
If the cable connector itself is maintained outside the sterile field, the cable connector need not be disinfected. However, this requires a person outside the sterile field to handle the connection of the probe to the associated equipment (or to an intermediate cable, if used) while a surgeon or other person within the sterile field is obliged to handle the sterilized probe end.
Another possibility is to encase the probe itself in a thin rubber or plastic sheath, thus preventing the patient from being touched by a nondisinfected probe. However, this solution is not satisfactory in connection with ultrasonic probes, wherein direct connection of the transducer to the tissue to be imaged is important. This solution is also useless in connection with probes providing aspiration or irrigation, requiring one or more lumens in communication with the probe head, nor where an optical image must be formed, as the sheath would interfere with optical transmission. Further, it appears likely that in the near future even devices that are sheathed in use will be required to be disinfected.
More specifically, disinfection is commonly accomplished by immersing the probe head and cable, using a "high-level" disinfectant, such as that sold as "Cidex", in an open tray for ten to thirty minutes prior to use, while allowing the cable connector, with the contact elements exposed, to simply remain outside the tray. Sterilization is accomplished similarly, but involves a much longer period of exposure to the disinfectant, typically ten to 24 hours. Both involve the difficulties mentioned above, namely, that the connector can be damaged if accidentally exposed to the disinfectant, and that two persons are required to make the connection of the equipment to an external instrument, power supply or the like.
Alternatively, delicate electronic surgical equipment that cannot withstand high temperature sterilization can be sterilized by exposure to ethylene oxide (EtO). The internal and external surfaces of the equipment are exposed to the EtO gas, and are then evacuated as necessary. While this gas does not damage or corrode the electrical connectors used, its use has several inherent difficulties. First, EtO is toxic, such that government regulations restrict its use. EtO is also commonly mixed with freon, to reduce its explosiveness; freon is in the process of being banned. Further, EtO sterilization is very time-consuming.
More recently, there have been developed self-contained sterilization units (see U.S. Pat. No. 5,225,160 to Sanford et al) that are capable of sterilizing various sorts of equipment in a convenient and rapid fashion. In use of these units, the equipment to be sterilized is disposed in a sealable chamber, and the interior and exterior surfaces thereof are exposed to a liquid chemical sterilant, under controlled temperature and pressure conditions, followed by a controlled water rinsing step. However, this system cannot be used without exposing the entire device to be sterilized to the sterilant, and thus is not useful for sterilizing electronic instruments having unprotected connectors for connection to external devices. As noted, simply providing a cap for the connector is insufficiently reliable to solve this problem.
Therefore, it is apparent that there exists a need for an efficient and convenient method of disinfecting an electronic probe comprising a probe head connected by a multiple-conductor cable to a multi-pin connector for connection to external equipment, such that the entire probe including the connector can be disinfected simultaneously, including any lumens and internal surfaces of the probe, without exposing the contact pins of the multi-pin connector to the disinfecting medium.
The following patents relate generally to the subject of disinfection of surgical or dental equipment.
Wappler U.S. Pat. No. 1,861,768 shows a basic "fumigating" sterilizer unit, including a sealed chamber having internal gas outlets for connection to the interior of catheters and the like.
Steinbock U.S. Pat. No. 2,786,245 shows a sterilizer tray including hollow posts for holding dental handpieces upright for drainage after sterilization. The dental tray is perforated to allow it to be lowered into a sterilizing fluid or the like. A second Steinbock U.S. Pat. No. 2,806,123, is generally similar.
U.S. Pat. No. 5,120,512 to Masuda recognizes the difficulty of sterilizing a precision instrument such as a dental handpiece using steam or ethylene oxide gas, and shows a ozonating chamber for bacteriostatic purposes. Various devices may be connected to mating fittings for sterilizing their interior passages.
U.S. Pat. No. 5,137,689 to Cantrell shows a sterilizing device wherein instruments are connected by pressure fittings to receive pressurized sterilizing fluid for cleaning their internal surfaces.
U.S. Pat. No. 2,546,385 to Christina shows a custom-fitted tray for efficient receiving and cleaning of ampules for medicines and the like.
As noted above, U.S. Pat. No. 5,225,160 to Sanford et al shows a system for decontaminating and sterilizing medical instruments such as endoscopes, wherein an antimicrobial liquid may be sprayed on the exterior surface of the instrument and be supplied to the internal surfaces thereof.
As indicated above, the disinfection of an electronic probe used in surgical procedures presents a special problem not solved by the prior art patents discussed above.